(a) Field of the Invention
The present invention relates to a signal level display apparatus for displaying, in bar chart style or in dots, the levels of input signals by a plurality of light-emitting elements.
(b) Description of the Prior Art
As devices for displaying the levels of various input signals, there have been known, in addition to known voltmeters and oscilloscopes, those display devices having a row of a plurality of light-emitting elements such as light-emitting diodes to make stepwise illuminating display of the levels of input signals in the form of either bar chart or dots. FIG. 1 shows an example of such known signal level display devices. The illustrated signal level display device is arranged so that the level of an input signal applied to an input terminal 1 is displayed in the form of a bar chart on a display unit 3 having five LEDs 3a to 3e arranged in a row and driven by a display driving means 2. The display driving means 2 has five comparators 4a to 4e to which are applied reference voltages V.sub.1 to V.sub.5 (V.sub.1 &lt;V.sub.2 &lt;V.sub.3 &lt;V.sub.4 &lt;V.sub.5) as shown in FIG. 2. When an input signal voltage V.sub.in of, for example, V.sub.2 &lt;V.sub.in &lt;V.sub.3 is applied to an input terminal 1, the potentials at the respective output terminals of the comparators 4a and 4b are rendered to zero level so that the LEDs 3a and 3b are lighted up. Here, the relationship between the illumination of these LEDs 3a to 3e and the input signal voltage V.sub.in is illustrated in FIG. 3.
The display device of this known type is designed so as to effect a display in stepwise mode in accordance with the level of the input signal. Accordingly, especially in case the level of the input signal lies at an intermediate value between the threshold values (i.e. the aforesaid voltages V.sub.1 to V.sub.5) of those LEDs representing the respective steps in the row, there arises the disadvantage that the level of the input signal cannot be displayed correctly.